The invention relates to a machine for perforating corrugated tubing at accurately spaced locations. Such tubing is commonly used for drainage and is frequently of thermoplastic material.
One of the requirements in perforating corrugated tubing is that the perforations be made in the valleys between corrugations; if the requirement is not met the tubing is rendered unsuitable for its purpose. In practice it is difficult to ensure that the requirement is met, especially in the case of thermoplastic tubing which is being fed directly from an extruder and corrugating machine, because of variations in corrugation pitch during cooling and handling, and if the perforations are not accurately located in the valleys as required, a great deal of time and material may be wasted.
According to the present invention the perforations are made by cutters, and the tubing is clamped positively in relation to the cutters during each cutting stroke.
More particularly, a machine in accordance with the present invention comprises a machine frame structure on which are mounted means for advancing the tubing along a predetermined path in intermittent steps of equal length, releasable clamping means operable to clamp the tubing in a stationary position relative to the frame structure, a plurality of cutters each being operable to move through a cutting stroke lying in a plane which is transverse to said predetermined path and intersects a valley between adjacent corrugations of the tubing when the tubing is clamped in the stationary position, and sequencing means for controlling the sequence of machine operations. The sequencing means include means responsive to completion of a step of the advancing means for initiating movement of the clamping members into the clamping position, means operable in accordance with movement of the clamping members into the clamping position for initiating movement of the cutters through a cutting stroke, means responsive to completion of the cutting stroke for initiating release of the clamping means, and means responsive to return of the clamping members to the release positions for initiating a subsequent step of the advancing means.